Self-Assembly by 4D Printing: Design and Fabrication of Sequential Self-Folding

Abstract Folding-based self-assembly is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It has highly potential applications in packaging of solar cells and space structures. In this study, we present a sequential self-assembly design and fabrication approach that is realized by thermal activation of bilayer actuators and transforms two-dimensional nets into three-dimensional structures. The time-dependent behaviors and shape memory performances of each bilayer actuator via experimental methods are investigated. The relationship between structure design parameters of bilayer actuators and their correspondingly self-assembly speed has been studied. Our main findings the process parameters of 4D printing is a simple and effective design principle for controlling the speed of self-assembly. By properly designing the bilayer actuators, 3D printed structures with programmed bilayer actuators respond rapidly to a thermal stimulus, and self-fold to specified shapes in controlled shape changing sequences. A folding box structure is used as an example to illustrate the methodology, which normally requires a folding sequence in order to form a stable and fully packed structure. Measurements of the spatial and temporal nature of self-assembly structures are in good agreement with the desired configurations.